50% packet loss on LAN

[crwagner]

Hi all,

Ok, I've gone through here and read several of the threads relating to network problems, but still can't seem to get my Gentoo box to work right. It used to be fine while running debian, but after a hard drive failure, I decided to get a new drive and install Gentoo.

While doing the install, all the networking worked just fine. Now however, I get excessive packet loss, which makes working with the machine a real bear (emerge [r]sync and wget/proz take many attempts). I've tried 2 different network cards (Tulip based and 3c590 based), 2 different ethernet cables, 2 different PCI slots, different ports on the switch, both 2.4.22 and 2.6.1 kernels, disabling acpi, tried noapic (but samba wouldn't start then).

When I boot up with a LiveCD, I get 0% packet loss, however, when I use the compiled kernel, I end up with 40-60% packet loss (when testing with 100-300 packets) pinging other hosts on my lan segment (which can ping each other with 0% packet loss). In all this time, I've only seen a max of 1 error, 2 overruns, and 10 collisions. While trying different transmission speeds (via mii-diag), I've seen the carrier stat in ipconfig slowly climb while using 10BaseT-FD, but not during 100BaseTx-FD or 10BaseT-HD. Once an SSH session is established, it will stay up, despite pings not going through (I can check the pings via SSH without problem, but it will drop packets back to the machine estabilishing the SSH connection. The drops always happen in blocks (i.e. icmp_seq 1-32 get responses, 33-47 drop (with no error messages, merely no reply), 48-63 get responeses...etc).

I do know quite a bit about linux, however, lower level networking is my weakest area.

Relevant lines from my latest attempts at the 2.6.1-gentoo kernel config

[dogshu]

You should make sure you're using a decent network cable... CAT5 or CAT5e is good, CAT3 is bad.

[crwagner]

[bbringle]

I compiled gentoo a few days ago on my home computer and experienced the same network problems (drops and errors) with the default 2.4.22-r5 gen kernel.

As a fix, I recompiled my kernel to remove the IPv6 and IPSec stuff, which I don't use, and the problems all went away No drops or errors anymore.

However,
I'm not sure if the blame can be put on a poor kernel or poor networking equipment... as when I direct connected my NIC to the cable modem the networking with the gen kernel worked fine. I only had network problems when I connected through my $30 D-Link router.

I suggest removing the IPv6 from your kernel configuration if it is not necessary for operations.